diff -r 7152559e3d08 -r 892c29484414 src/lemon/lemon_reader.h
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/src/lemon/lemon_reader.h	Mon May 09 11:24:26 2005 +0000
@@ -0,0 +1,977 @@
+/* -*- C++ -*-
+ * src/lemon/lemon_reader.h - Part of LEMON, a generic C++ optimization library
+ *
+ * Copyright (C) 2005 Egervary Jeno Kombinatorikus Optimalizalasi Kutatocsoport
+ * (Egervary Research Group on Combinatorial Optimization, EGRES).
+ *
+ * Permission to use, modify and distribute this software is granted
+ * provided that this copyright notice appears in all copies. For
+ * precise terms see the accompanying LICENSE file.
+ *
+ * This software is provided "AS IS" with no warranty of any kind,
+ * express or implied, and with no claim as to its suitability for any
+ * purpose.
+ *
+ */
+
+///\ingroup io_group
+///\file
+///\brief Lemon Format reader.
+
+#ifndef LEMON_LEMON_READER_H
+#define LEMON_LEMON_READER_H
+
+#include <iostream>
+#include <fstream>
+#include <string>
+#include <vector>
+#include <algorithm>
+#include <map>
+#include <memory>
+
+#include <lemon/error.h>
+#include "item_reader.h"
+
+
+namespace lemon {
+
+  /// \addtogroup io_group
+  /// @{
+
+  /// \brief Lemon Format reader class.
+  /// 
+  class LemonReader {
+  private:
+    
+    class FilterStreamBuf : public std::streambuf {
+    public:
+
+      typedef std::streambuf Parent;
+      typedef Parent::char_type char_type;
+      FilterStreamBuf(std::istream& is, int& num) 
+	: _is(is), _base(0), _eptr(0), 
+	  _num(num), skip_state(after_endl) {}
+
+    protected:
+
+      enum skip_state_type {
+	no_skip,
+	after_comment,
+	after_endl,
+	empty_line
+      };
+
+      char_type small_buf[1];
+
+
+      std::istream& _is;
+
+      char_type* _base;
+      char_type* _eptr;
+
+      int& _num;
+
+      skip_state_type skip_state;
+
+
+      char_type* base() { return _base; }
+
+      char_type* eptr() { return _eptr; }
+
+      int blen() { return _eptr - _base; }
+
+      void setb(char_type* buf, int len) {
+	_base = buf;
+	_eptr = buf + len;
+      }
+  
+      virtual std::streambuf* setbuf(char *buf, int len) {
+	if (base()) return 0;
+	if (buf != 0 && len >= (int)sizeof(small_buf)) {
+	  setb(buf, len);
+	} else {
+	  setb(small_buf, sizeof(small_buf));
+	}
+	setg(0, 0, 0);
+	return this;
+      }
+
+      bool put_char(char c) {
+	switch (skip_state) {
+	case no_skip:
+	  switch (c) {
+	  case '\n': 
+	    skip_state = after_endl;
+	    return true;
+	  case '#':
+	    skip_state = after_comment;
+	    return false;
+	  default:
+	    return true;
+	  }
+	case after_comment:
+	  switch (c) {
+	  case '\n': 
+	    skip_state = after_endl;
+	    return true;
+	  default:
+	    return false;
+	  }        
+	case after_endl:
+	  switch (c) {
+	  case '@':
+	    return false;
+	  case '\n': 
+	    return false;
+	  case '#':
+	    skip_state = empty_line;
+	    return false;
+	  default:
+	    if (!isspace(c)) {
+	      skip_state = no_skip;
+	      return true;
+	    } else {
+	      return false;
+	    }
+	  }
+	  break;
+	case empty_line:
+	  switch (c) {
+	  case '\n': 
+	    skip_state = after_endl;
+	    return false;
+	  default:
+	    return false;
+	  }
+	}
+	return false;
+      }
+
+      virtual int underflow() {
+	char c;
+	if (_is.read(&c, 1)) {
+	  _is.putback(c);
+	  if (c == '@') {
+	    return EOF;
+	  }
+	} else {
+	  return EOF;
+	}
+	char_type *ptr;
+	for (ptr = base(); ptr != eptr(); ++ptr) {
+	  if (_is.read(&c, 1)) {
+	    if (c == '\n') ++_num;
+	    if (put_char(c)) {
+	      *ptr = c;
+	    } else {
+	      if (skip_state == after_endl && c == '@') {
+		_is.putback('@');
+		break;
+	      }
+	      --ptr;
+	    }
+	  } else {
+	    break;
+	  }
+	}
+	setg(base(), base(), ptr);
+	return *base();
+      }
+
+      virtual int sync() {
+	return EOF;
+      }
+    };
+
+  public:
+
+    class SectionReader {
+    public:
+      /// \e
+      virtual bool header(const std::string& line) = 0;
+      /// \e
+      virtual void read(std::istream& is) = 0;
+    };
+
+    /// \e
+    LemonReader(std::istream& _is) 
+      : is(&_is), own_is(false) {}
+
+    LemonReader(const std::string& filename) 
+      : is(0), own_is(true) {
+      is = new std::ifstream(filename.c_str());
+    }
+
+
+    ~LemonReader() {
+      if (own_is) {
+	delete is;
+      }
+    }
+
+  private:
+    LemonReader(const LemonReader&);
+    void operator=(const LemonReader&);
+
+  public:
+    
+    /// \e
+    void attach(SectionReader& reader) {
+      readers.push_back(&reader);
+    }
+
+    /// \e
+    void detach(SectionReader& reader) {
+      std::vector<SectionReader*>::iterator it = 
+	std::find(readers.begin(), readers.end(), &reader);
+      if (it != readers.end()) {
+	readers.erase(it);
+      }
+    }
+
+    /// \e
+    void run() {
+      int line_num = 0;
+      std::string line;
+      try {
+	while ((++line_num, getline(*is, line)) && line.find("@end") != 0) {
+	  SectionReaders::iterator it;
+	  for (it = readers.begin(); it != readers.end(); ++it) {
+	    if ((*it)->header(line)) {
+	      char buf[2048];
+	      FilterStreamBuf buffer(*is, line_num);
+	      buffer.pubsetbuf(buf, sizeof(buf));
+	      std::istream is(&buffer);
+	      (*it)->read(is);
+	      break;
+	    }
+	  }
+	}
+      } catch (DataFormatError& error) {
+	error.line(line_num);
+	throw error;
+      }	
+    }
+
+
+  private:
+
+    std::istream* is;
+    bool own_is;
+
+    typedef std::vector<SectionReader*> SectionReaders;
+    SectionReaders readers;
+
+  };
+
+
+  /// \e
+  class CommonSectionReaderBase : public LemonReader::SectionReader {
+  protected:
+    template <typename _Item>
+    class ReaderBase;
+    
+    template <typename _Item>
+    class InverterBase : public ReaderBase<_Item> {
+    public:
+      typedef _Item Item;
+      virtual void read(std::istream&, const Item&) = 0;
+      virtual Item read(std::istream&) const = 0;
+
+      virtual InverterBase<_Item>* getInverter() {
+	return this;
+      }
+
+
+    };
+
+    template <typename _Item, typename _Map, typename _Reader>
+    class MapReaderInverter : public InverterBase<_Item> {
+    public:
+      typedef _Item Item;
+      typedef _Reader Reader;
+      typedef typename Reader::Value Value;
+      typedef _Map Map;
+      typedef std::map<Value, Item> Inverse;
+
+      Map& map;
+      Reader reader;
+      Inverse inverse;
+
+      MapReaderInverter(Map& _map, const Reader& _reader) 
+	: map(_map), reader(_reader) {}
+
+      virtual ~MapReaderInverter() {}
+
+      virtual void read(std::istream& is, const Item& item) {
+	Value value;
+	reader.read(is, value);
+	map.set(item, value);
+	typename Inverse::iterator it = inverse.find(value);
+	if (it == inverse.end()) {
+	  inverse.insert(std::make_pair(value, item));
+	} else {
+	  throw DataFormatError("Multiple ID occurence");
+	}
+      }
+
+      virtual Item read(std::istream& is) const {
+	Value value;
+	reader.read(is, value);	
+	typename Inverse::const_iterator it = inverse.find(value);
+	if (it != inverse.end()) {
+	  return it->second;
+	} else {
+	  throw DataFormatError("Invalid ID error");
+	}
+      }      
+
+    };
+
+    template <typename _Item, typename _Reader>
+    class SkipReaderInverter : public InverterBase<_Item> {
+    public:
+      typedef _Item Item;
+      typedef _Reader Reader;
+      typedef typename Reader::Value Value;
+      typedef std::map<Value, Item> Inverse;
+
+      Reader reader;
+
+      SkipReaderInverter(const Reader& _reader) 
+	: reader(_reader) {}
+
+      virtual ~SkipReaderInverter() {}
+
+      virtual void read(std::istream& is, const Item& item) {
+	Value value;
+	reader.read(is, value);
+	typename Inverse::iterator it = inverse.find(value);
+	if (it == inverse.end()) {
+	  inverse.insert(std::make_pair(value, item));
+	} else {
+	  throw DataFormatError("Multiple ID occurence error");
+	}
+      }
+
+      virtual Item read(std::istream& is) const {
+	Value value;
+	reader.read(is, value);	
+	typename Inverse::const_iterator it = inverse.find(value);
+	if (it != inverse.end()) {
+	  return it->second;
+	} else {
+	  throw DataFormatError("Invalid ID error");
+	}
+      }
+
+    private:
+      Inverse inverse;
+    };
+
+    // Readers
+
+    template <typename _Item>    
+    class ReaderBase {
+    public:
+      typedef _Item Item;
+
+      virtual ~ReaderBase() {}
+
+      virtual void read(std::istream& is, const Item& item) = 0;
+      virtual InverterBase<_Item>* getInverter() = 0;
+    };
+
+    template <typename _Item, typename _Map, typename _Reader>
+    class MapReader : public ReaderBase<_Item> {
+    public:
+      typedef _Map Map;
+      typedef _Reader Reader;
+      typedef typename Reader::Value Value;
+      typedef _Item Item;
+      
+      Map& map;
+      Reader reader;
+
+      MapReader(Map& _map, const Reader& _reader) 
+	: map(_map), reader(_reader) {}
+
+      virtual ~MapReader() {}
+
+      virtual void read(std::istream& is, const Item& item) {
+	Value value;
+	reader.read(is, value);
+	map.set(item, value);
+      }
+
+      virtual InverterBase<_Item>* getInverter() {
+	return new MapReaderInverter<Item, Map, Reader>(map, reader);
+      }
+    };
+
+
+    template <typename _Item, typename _Reader>
+    class SkipReader : public ReaderBase<_Item> {
+    public:
+      typedef _Reader Reader;
+      typedef typename Reader::Value Value;
+      typedef _Item Item;
+
+      Reader reader;
+      SkipReader(const Reader& _reader) : reader(_reader) {}
+
+      virtual ~SkipReader() {}
+
+      virtual void read(std::istream& is, const Item&) {
+	Value value;
+	reader.read(is, value);
+      }      
+
+      virtual InverterBase<Item>* getInverter() {
+	return new SkipReaderInverter<Item, Reader>(reader);
+      }
+    };
+
+    template <typename _Item>
+    class ResolverReaderBase {
+    public:
+      typedef _Item Item;
+      virtual Item resolve(std::istream& is) const = 0;
+    };
+
+    template <typename _Item, typename _Resolver>
+    class ResolverReader : public ResolverReaderBase<_Item> {
+    public:
+      typedef _Item Item;
+      typedef _Resolver Resolver;
+
+      const Resolver& resolver;
+
+      ResolverReader(const Resolver& _resolver) 
+	: resolver(_resolver) {}
+
+      virtual Item resolve(std::istream& is) const {
+	return resolver.resolve(is);
+      }
+    };
+
+    class ValueReaderBase {
+    public:
+      virtual void read(std::istream&) {};
+    };
+
+    template <typename _Value, typename _Reader>
+    class ValueReader : public ValueReaderBase {
+    public:
+      typedef _Value Value;
+      typedef _Reader Reader;
+
+      ValueReader(Value& _value, const Reader& _reader)
+ 	: value(_value), reader(_reader) {}
+
+      virtual void read(std::istream& is) {
+	reader.read(is, value);
+      }
+    private:
+      Value& value;
+      Reader reader;
+    };
+    
+  };
+
+
+  template <typename _Graph, typename _Traits = DefaultReaderTraits>
+  class NodeSetReader : public CommonSectionReaderBase {
+    typedef CommonSectionReaderBase Parent;
+  public:
+
+    typedef _Graph Graph;
+    typedef _Traits Traits;
+    typedef typename Graph::Node Item;
+    typedef typename Traits::Skipper DefaultSkipper;
+
+    NodeSetReader(LemonReader& _reader, Graph& _graph, 
+		  const std::string& _id = std::string(),
+		  const DefaultSkipper& _defreader = DefaultSkipper()) 
+      : graph(_graph), id(_id), skipper(_defreader) {
+      _reader.attach(*this);
+    } 
+
+    virtual ~NodeSetReader() {
+      for (typename MapReaders::iterator it = readers.begin(); 
+	   it != readers.end(); ++it) {
+	delete it->second;
+      }
+    }
+
+  private:
+    NodeSetReader(const NodeSetReader&);
+    void operator=(const NodeSetReader&);
+  
+  public:
+
+    /// \brief Add a new node map reader command for the reader.
+    ///
+    /// Add a new node map reader command for the reader.
+    template <typename Map>
+    NodeSetReader& readMap(std::string name, Map& map) {
+      return readMap<typename Traits::
+	template Reader<typename Map::Value>, Map>(name, map);
+    }
+
+    /// \brief Add a new node map reader command for the reader.
+    ///
+    /// Add a new node map reader command for the reader.
+    template <typename Reader, typename Map>
+    NodeSetReader& readMap(std::string name, Map& map, 
+			     const Reader& reader = Reader()) {
+      if (readers.find(name) != readers.end()) {
+	ErrorMessage msg;
+	msg << "Multiple read rule for node map: " << name;
+	throw IOParameterError(msg.message());
+      }
+      readers.insert(
+	make_pair(name, new MapReader<Item, Map, Reader>(map, reader)));
+      return *this;
+    }
+
+    /// \brief Add a new node map skipper command for the reader.
+    ///
+    /// Add a new node map skipper command for the reader.
+    template <typename Reader>
+    NodeSetReader& skipMap(std::string name, 
+			   const Reader& reader = Reader()) {
+      if (readers.find(name) != readers.end()) {
+	ErrorMessage msg;
+	msg << "Multiple read rule for node map: " << name;
+	throw IOParameterError(msg.message());
+      }
+      readers.insert(make_pair(name, new SkipReader<Item, Reader>(reader)));
+      return *this;
+    }
+
+    /// \e
+    virtual bool header(const std::string& line) {
+      std::istringstream ls(line);
+      std::string command;
+      std::string name;
+      ls >> command >> name;
+      return command == "@nodeset" && name == id;
+    }
+
+    /// \e
+    virtual void read(std::istream& is) {
+      std::vector<ReaderBase<Item>* > index;
+      std::string line;
+
+      getline(is, line);
+      std::istringstream ls(line);	
+      while (ls >> id) {
+	typename MapReaders::iterator it = readers.find(id);
+	if (it != readers.end()) {
+	  index.push_back(it->second);
+	} else {
+	  index.push_back(&skipper);
+	}
+	if (id == "id" && inverter.get() == 0) {
+	  inverter.reset(index.back()->getInverter());
+	  index.back() = inverter.get();
+	}
+      }
+      while (getline(is, line)) {	
+	typename Graph::Node node = graph.addNode();
+	std::istringstream ls(line);
+	for (int i = 0; i < (int)index.size(); ++i) {
+	  index[i]->read(ls, node);
+	}
+      }
+    }
+
+    bool isResolver() const {
+      return inverter.get() != 0;
+    }
+
+    typename Graph::Node resolve(std::istream& is) const {
+      return inverter->read(is);
+    } 
+
+  private:
+
+    typedef std::map<std::string, ReaderBase<Item>*> MapReaders;
+    MapReaders readers;
+   
+    Graph& graph;   
+    std::string id;
+    SkipReader<Item, DefaultSkipper> skipper;
+
+    std::auto_ptr<InverterBase<Item> > inverter;
+  };
+
+
+ 
+  /// \e
+  template <typename _Graph, typename _Traits = DefaultReaderTraits>
+  class EdgeSetReader : public CommonSectionReaderBase {
+    typedef CommonSectionReaderBase Parent;
+  public:
+
+    typedef _Graph Graph;
+    typedef _Traits Traits;
+    typedef typename Graph::Edge Item;
+    typedef typename Traits::Skipper DefaultSkipper;
+
+    template <typename Resolver>
+    EdgeSetReader(LemonReader& _reader, Graph& _graph, 
+		  const Resolver& _nodeResolver, 
+		  const std::string& _id = std::string(),
+		  const DefaultSkipper& _defreader = DefaultSkipper()) 
+      : graph(_graph), id(_id), skipper(_defreader),
+      nodeResolver(new ResolverReader<typename Graph::Node, Resolver>
+		   (_nodeResolver)) {
+      _reader.attach(*this);
+    } 
+
+    virtual ~EdgeSetReader() {
+      for (typename MapReaders::iterator it = readers.begin(); 
+	   it != readers.end(); ++it) {
+	delete it->second;
+      }
+    }
+
+  private:
+    EdgeSetReader(const EdgeSetReader&);
+    void operator=(const EdgeSetReader&);
+
+  public:
+
+    /// \brief Add a new node map reader command for the reader.
+    ///
+    /// Add a new node map reader command for the reader.
+    template <typename Map>
+    EdgeSetReader& readMap(std::string name, Map& map) {
+      return readMap<typename Traits::
+	template Reader<typename Map::Value>, Map>(name, map);
+    }
+
+    /// \brief Add a new node map reader command for the reader.
+    ///
+    /// Add a new node map reader command for the reader.
+    template <typename Reader, typename Map>
+    EdgeSetReader& readMap(std::string name, Map& map, 
+			     const Reader& reader = Reader()) {
+      if (readers.find(name) != readers.end()) {
+	ErrorMessage msg;
+	msg << "Multiple read rule for edge map: " << name;
+	throw IOParameterError(msg.message());
+      }
+      readers.insert(
+	make_pair(name, new MapReader<Item, Map, Reader>(map, reader)));
+      return *this;
+    }
+
+    /// \brief Add a new node map skipper command for the reader.
+    ///
+    /// Add a new node map skipper command for the reader.
+    template <typename Reader>
+    EdgeSetReader& skipMap(std::string name, 
+			   const Reader& reader = Reader()) {
+      if (readers.find(name) != readers.end()) {
+	ErrorMessage msg;
+	msg << "Multiple read rule for node map: " << name;
+	throw IOParameterError(msg.message());
+      }
+      readers.insert(make_pair(name, new SkipReader<Item, Reader>(reader)));
+      return *this;
+    }
+
+    /// \e
+    virtual bool header(const std::string& line) {
+      std::istringstream ls(line);
+      std::string command;
+      std::string name;
+      ls >> command >> name;
+      return command == "@edgeset" && name == id;
+    }
+
+    /// \e
+    virtual void read(std::istream& is) {
+      std::vector<ReaderBase<Item>* > index;
+      std::string line;
+
+      getline(is, line);
+      std::istringstream ls(line);	
+      while (ls >> id) {
+	typename MapReaders::iterator it = readers.find(id);
+	if (it != readers.end()) {
+	  index.push_back(it->second);
+	} else {
+	  index.push_back(&skipper);
+	}
+	if (id == "id" && inverter.get() == 0) {
+	  inverter.reset(index.back()->getInverter());
+	  index.back() = inverter.get();
+	}
+      }
+      while (getline(is, line)) {	
+	std::istringstream ls(line);
+	typename Graph::Node from = nodeResolver->resolve(ls);
+	typename Graph::Node to = nodeResolver->resolve(ls);
+	typename Graph::Edge edge = graph.addEdge(from, to);
+	for (int i = 0; i < (int)index.size(); ++i) {
+	  index[i]->read(ls, edge);
+	}
+      }
+    }
+
+    bool isResolver() const {
+      return inverter.get() != 0;
+    }
+
+    typename Graph::Edge resolve(std::istream& is) {
+      return inverter->read(is);
+    } 
+
+  private:
+
+    typedef std::map<std::string, ReaderBase<Item>*> MapReaders;
+    MapReaders readers;
+   
+    Graph& graph;   
+    std::string id;
+    SkipReader<Item, DefaultSkipper> skipper;
+
+    std::auto_ptr<InverterBase<Item> > inverter;
+    std::auto_ptr<ResolverReaderBase<typename Graph::Node> > nodeResolver;
+  };
+
+
+  /// \e
+  template <typename _Traits = DefaultReaderTraits>
+  class AttributeReader : public CommonSectionReaderBase {
+    typedef CommonSectionReaderBase Parent;
+    typedef _Traits Traits; 
+  public:
+    /// \e
+    AttributeReader(LemonReader& _reader, 
+		    const std::string& _id = std::string()) : id(_id) {
+      _reader.attach(*this);
+    }
+
+    /// \e
+    virtual ~AttributeReader() {
+      for (typename Readers::iterator it = readers.begin(); 
+	   it != readers.end(); ++it) {
+	delete it->second;
+      }
+    }
+
+  private:
+    AttributeReader(const AttributeReader&);
+    void operator=(AttributeReader&);
+
+  public:
+    /// \e
+    template <typename Value>
+    AttributeReader& readAttribute(const std::string& id, Value& value) {
+      return readAttribute<typename Traits::template Reader<Value> >
+	(id, value);
+    }
+
+    /// \e
+    template <typename Reader, typename Value>
+    AttributeReader& readAttribute(const std::string& name, Value& value,
+				   const Reader& reader = Reader()) {
+      if (readers.find(name) != readers.end()) {
+	ErrorMessage msg;
+	msg << "Multiple read rule for attribute: " << name;
+	throw IOParameterError(msg.message());
+      }
+      readers.insert(make_pair(name, new ValueReader<Value, Reader>
+      			       (value, reader)));
+      return *this;
+    }
+
+    /// \e
+    bool header(const std::string& line) {
+      std::istringstream ls(line);
+      std::string command;
+      std::string name;
+      ls >> command >> name;
+      return command == "@attributes" && name == id;
+    }
+
+    /// \e
+    void read(std::istream& is) {
+      std::string line;
+      while (getline(is, line)) {
+	std::istringstream ls(line);
+	std::string id;
+	ls >> id;
+	typename Readers::iterator it = readers.find(id);
+	if (it != readers.end()) {
+	  it->second->read(ls);
+	}
+      }
+    }    
+
+  private:
+    std::string id;
+
+    typedef std::map<std::string, ValueReaderBase*> Readers;
+    Readers readers;
+  
+  };
+
+  template <typename _Graph>
+  class NodeReader : public CommonSectionReaderBase {
+    typedef CommonSectionReaderBase Parent;
+    typedef _Graph Graph;
+    typedef typename Graph::Node Item;
+  public:
+    
+    template <typename Resolver>
+    NodeReader(LemonReader& _reader, const Resolver& _resolver, 
+	       const std::string& _id = std::string()) 
+      : id(_id), resolver(new ResolverReader<typename Graph::Node, Resolver>
+		     (_resolver)) {
+      _reader.attach(*this);
+    } 
+
+    virtual ~NodeReader() {}
+
+  private:
+    NodeReader(const NodeReader&);
+    void operator=(const NodeReader&);
+
+  public:
+
+    void readNode(const std::string& name, Item& item) {
+      if (readers.find(name) != readers.end()) {
+	ErrorMessage msg;
+	msg << "Multiple read rule for node: " << name;
+	throw IOParameterError(msg.message());
+      }
+      readers.insert(make_pair(name, &item));
+    }
+
+    virtual bool header(const std::string& line) {
+      std::istringstream ls(line);
+      std::string command;
+      std::string name;
+      ls >> command >> name;
+      return command == "@nodes" && name == id;
+    }
+
+    virtual void read(std::istream& is) {
+      std::string line;
+      while (getline(is, line)) {
+	std::istringstream ls(line);
+	std::string id;
+	ls >> id;
+	typename ItemReaders::iterator it = readers.find(id);
+	if (it != readers.end()) {
+	  *(it->second) = resolver->resolve(ls); 
+	}	
+      }
+    }
+    
+  private:
+
+    std::string id;
+
+    typedef std::map<std::string, Item*> ItemReaders;
+    ItemReaders readers;
+    std::auto_ptr<ResolverReaderBase<Item> > resolver;
+  };
+
+  template <typename _Graph>
+  class EdgeReader : public CommonSectionReaderBase {
+    typedef CommonSectionReaderBase Parent;
+    typedef _Graph Graph;
+    typedef typename Graph::Edge Item;
+  public:
+    
+    template <typename Resolver>
+    EdgeReader(LemonReader& _reader, const Resolver& _resolver, 
+	       const std::string& _id = std::string()) 
+      : id(_id), resolver(new ResolverReader<typename Graph::Node, Resolver>
+		     (_resolver)) {
+      _reader.attach(*this);
+    } 
+
+    virtual ~EdgeReader() {}
+  private:
+    EdgeReader(const EdgeReader&);
+    void operator=(const EdgeReader&);
+
+  public:
+
+    void readEdge(const std::string& name, Item& item) {
+      if (readers.find(name) != readers.end()) {
+	ErrorMessage msg;
+	msg << "Multiple read rule for edge: " << name;
+	throw IOParameterError(msg.message());
+      }
+      readers.insert(make_pair(name, &item));
+    }
+
+
+    virtual bool header(const std::string& line) {
+      std::istringstream ls(line);
+      std::string command;
+      std::string name;
+      ls >> command >> name;
+      return command == "@nodes" && name == id;
+    }
+
+    virtual void read(std::istream& is) {
+      std::string line;
+      while (getline(is, line)) {
+	std::istringstream ls(line);
+	std::string id;
+	ls >> id;
+	typename ItemReaders::iterator it = readers.find(id);
+	if (it != readers.end()) {
+	  *(it->second) = resolver->resolve(ls); 
+	}	
+      }
+    }
+    
+  private:
+
+    std::string id;
+
+    typedef std::map<std::string, Item*> ItemReaders;
+    ItemReaders readers;
+    std::auto_ptr<ResolverReaderBase<Item> > resolver;
+  };
+
+  /// \e
+  class PrintReader : public LemonReader::SectionReader {
+    typedef LemonReader::SectionReader Parent;
+  public:
+
+    /// \e
+    PrintReader(LemonReader& reader) {
+      reader.attach(*this);
+    }
+
+    /// \e
+    bool header(const std::string& line) {
+      std::cout << "Asked header: " << line << std::endl; 
+      return true;
+    }
+
+    /// \e
+    void read(std::istream& is) {
+      std::string line;
+      while (std::getline(is, line)) {
+	std::cout << line << std::endl;
+      }
+    }
+  
+  };
+
+  /// @}
+}
+#endif